Equilibrium phase of high-entropy FeCoNiCrCu0.5 alloy at elevated temperature

The phase transformations of FeCoNiCrCu0.5 alloy with the as-cast structure and heat-treated structures were studied. The as-cast alloy specimens were first heated at 1050 °C with a holding time of 1 h. Serial heat-treatment processes at 350 °C, 500 °C, 650 °C, 800 °C, 950 °C, 1100 °C, 1250 °C and 1350 °C with a holding time of 24 h were then carried out to understand the phase evolution and the relationship between the microstructure and the hardness of the specimens. The microstructures were investigated and chemical analyses performed by optical microscopy (OM), scanning elector microscopy (SEM), X-ray diffractometer (XRD) and transmission elector microscopy (TEM). The results show that FCC peaks were observed from the X-ray diffraction of the as-cast specimens and a precipitate phase was present in the specimens that had been heated to 950 °C. The hardness of the FeCoNiCrCu0.5 alloy remained unchanged in the specimens that underwent various heat treatments that were applied in this study.